Generally, a Battery Management System (BMS) for a hybrid vehicle measures the voltage, current and temperature of a battery and performs a battery information prediction function and a battery control function, which are required for a Hybrid vehicle Control Unit (HCU), in order to apply a high voltage battery to the vehicle.
Conventionally, the calculation of the State Of Charge (SOC) of the battery is performed using the following Equation 1:
                              SOC          ⁡                      [            n            ]                          =                              SOC            ⁡                          [                              n                -                1                            ]                                -                                                                      ∑                                      n                    -                    1                                    n                                ⁢                I                                                                                                                                Ah                        basic                                            ×                                              Efficiency                        n                                            ×                                                                                                                                  AgingFactor                      n                                                                                            ×                          100              ⁡                              [                %                ]                                                                        (        1        )            wherein I is the charge or discharge current of the battery, SOC is the state of charge, Ah_basic is the reference capacity (rated capacity) of the battery, Efficiencyn is the efficiency of the battery depending on temperature, and AgingFactorn is the aging factor of the battery.
As shown in Equation 1, the SOC[n] of the battery is calculated in consideration of the accumulated charge and discharge current amounts per unit time, the State Of Health (SOH) efficiency, that is, efficiency depending on temperature, the aging factor of the battery, and the initial reference capacity (rated capacity), with reference to a previous SOC[n−1]. However, the aging factor indicates only the lifetime of a consumable battery and actually available capacity, so that it is impossible to precisely know the aging factor during operation after the installation of the battery in the vehicle.
Although, conventionally, an aging factor has been estimated in consideration of the total use time and the total accumulated current amount after the installation of a new battery in a vehicle, the aging factor is uniformly calculated without taking into account the characteristics of the battery, which vary depending on the operating temperature of the battery, the charge and discharge current amounts, and the user's operating conditions, so that there is a problem in that the control of the battery is unreliable.